Hydrocracking of polynuclear hydrocarbons



NOV. 28, 1967 W ET AL 3,355,376

HYDROCRACKING OF POLYNUCLEAR HYDROCARBON S Filed Nov. 15, 1965 2 Sheets-Sheet 1 Coal extract Regenerated catalyst Spent catalyst REGENERATION ZONE Fg HCI free gas to 52 product recovery Zinc oxide-rich ZnCl v 2 Spent catalyst 2 INVENTORS: Everett Gorin Clyde W. Zielke Robert T. Struck Nov. 28, 1967 t 5. en; ET AL 3,355,376

HYDROCRACKING OF POLYNUCLEAR HYDROCARBONS Filed Nov. 15, 1965 2 Sheets-Sheet 2 Flue gas 74 Regenerated catalyst Steam '[D A \50 Spent catalyst Air in Spent catalyst Preheated air make-up /30 1-96 ZnCl Zn slurry in ZnCl Fig. 4.

INVENTO/PS:

Everett Gorin Clyde w. Zielke Robert T. Struck United States Patent 3,355,376 HYDROCRACIGNG 0F POLYNUCLEAR HYDROCARBONS Everett Gorin, Pittsburgh, Robert T. Struck, Bridgeville, and Clyde W. Zielke, Pittsburgh, Pa., assignors, by mesne assignments, of one-half to Consolidation Coal Company, a corporation of Delaware, and one-half to the United States of America as represented by the Secretary of the Interior Filed Nov. 15, 1965, Ser. No. 507,970 9 Claims. (Cl. 208) ABSTRACT OF THE DISCLOSURE Polynuclear aromatic hydrocarbons such as coal extract are hydrocracked in the presence of molten zinc halide and zinc oxide.

This invention relates to the catalytic hydrocracking of predominantly polynuclear aromatic hydrocarbonaceous materials, and particularly to the conversion to gasoline of substantially nondistillable high molecular weight predominantly polynuclear aromatic hydrocarbonaceous feedstocks which may contain appreciable quantities of nitrogen, oxygen and sulfur compounds, as well as unfilterable ash contaminants.

US. patent application Ser. No. 449,904, filed Apr. 21, 1965, describes such a process and utilizes as a catalyst molten zinc halides. This patent application sets forth that polynuclear hydrocarbons including but not limited to those which are nondistillable, may be readily converted to a low boiling liquid suitable as a fuel such as gasoline in the presence of a large quantity of molten zinc halide.

An object of this invention is to provide a process for hydrocracking polynuclear aromatic materials by contacting' a feedstock which is heavier than gasoline with hydrogen and a zinc halide salt at elevated temperatures. Another object of this invention is to provide this process with a zinc oxide acceptor for removing hydrogen chloride from the system. In particular it is an object of this invention to convert polynuclear aromatic hydrocarbonaceous material to gasoline in the presence of a catalytic-acceptor composition comprising zinc halide salt and zinc oxide in a mole ratio of at least ten parts halide to one part oxide.

These and other objects and features of the invention will be seen in the fol-lowing description and in the appended drawing, in which: 7

FIG. 1 is a schematic representation of the basic. process;

FIG. 2 shows the hydrocracking portion of the system; 7

and t FIGS. 3 and 4 show alternate embodiments of the regeneration steps for receiving spent catalyst.

The present invention is an improvement in the hydrocracking process described in the above-mentioned application. Accordingly, in order to understand the present invention, it is necessary to review the essential elements of the basic process. FIGURE 1 shows these schematically. For convenience in reference, zinc chloride, ZnCl is used as illustrative of the catalyst, and coal extract as illustrative of a sulfurand nitrogen-containing polynuclear hydrocarbon. Numeral 10 designates a suitable Hydrocracking Zone to which coal extract and hydrogen are fed through conduits 12 and 14, respectively. Regenerated molten zinc chloride is introduced through conduit 16 into the Hydrocracking Zone 10 from a Regeneration Zone 18. The operating conditions maintained in the Hydrocracking Zone 10 are as follows:

"ice

of hydrocarbon inventory in the Hydrocracking Zone.

The hydrocracked products, i.e., low boiling hydrocar bons, are withdrawn through a conduit 20. Spent catalyst is conducted to the Regeneration Zone 18 via a conduit 22.

Normally, the reactions occurring in the Hydrocracking Zone are as follows:

In accordance with the present invention, we have found that zinc oxide is extremely useful in the Hydrocracking Zone as an acceptor, as set forth in the following equation:

(4) ZnO+2HCl=ZnCl +H 0 By virtue of the use of zinc oxide, loss of HCl from the system is minimized, and corrosion by HCl is controlled. The use of zinc oxide also effectively eliminates the reaction expressed in Equation 3 above, thus making it unnecessary to regenerate ZnCl from ZnCl -NH Ol.

The amount of zinc oxide in the Hydrocracking Zone must be carefully regulated, since the catalytic effectiveness of the latter is seriously inhibited by excessive amounts. We have found that the zinc oxide concentration must be kept lower than a ZnO/ZnCl mol ratio of 0.10, and preferably below 0.05. Table I below shows the efiect of different molar ratio of ZnO to ZnC-l on the conversion of nondistillable coal extract to distillate, and also on the yield of low boiling gasoline stock, i.e., the C 200 C. portion of the distillate product.

TABLE I Run No 26 23 36 68 67 Temperature, C 427 427 427 399 399 Total Hot Pressure, P.s.i.g 4, 200 4, 200 4, 200 3, 000 3, 000 Residence Time, Min 60 60 60 60 60 Feed Gm.:

Extract 50. 0 50. 0 50. 0 50. 0 ZnClz 50. 0 50. 0 50. 0 100. 0 ZnO 25. 0 2. 2. 50 2. 50 ZnClz/Extract, Wt. Ratio 1. 0 1. 0 1. 0 2. 0 ZnO/ZnOlz, Moi Ratio 0. 84 0. 084 0. 084 0. 042 Yields, Wt. Percent MAF Fee 1-C3) 0 4. 6 10. 2 3.4 5. 9 5O l-ClHio 6 1. 5 6. 3 1. 4 5.9 Il-C4H1D 1. 6 0. 5 1. 1 0. 2 0. 9 C5X2OO O. Distillate" 60. 4 25. 5 42. 5 39.4 61. 0 200x400 C. Distillate 3.1 23.5 23.4 21.0 4.5 Hydrogen Consumed, Wt.

Percent MAF Feed 8.7 5.0 7.6 5.6 7.4 Conversion, Wt. Percent MA]? Feed 89.8 58. 8 84. 2 69. 0 79. 8

The following conclusions are evident from the data in the above Table I:

(1) High concentrations of ZnO severely inhibit the hydrocracking activity of ZnCl not only with regard to total conversion, but also with regard to cracking to gasoline (see Run No. 23).

(2) A ZnO/ZnCl mol ratio lower than 0.10, e.g., 0.084, is required to get a high conversion to distillate (see Run No. 36); and a ZnO/ZnCl mol ratio lower than 0.05, e.g., 0.042 is required to get a high yield of gasoline (i.e. C X200 C. distillate) (see Run No. 67).

FIGURE 2 shows schematically a hydrocracking system in which the molten zinc chloride catalyst is introduced as two separate streams, one as ZnCl without any zinc oxide, and the other as zinc oxide-rich ZnCl The 3 oxide-rich ZnCl is added to the latter stages of the hydrocracking system to remove the HCl.

The hydrocracking system comprises a plurality of hydrocracking vessels 30, each of which contains two Hydrocracking Zones 32 and 34, one above the other, so that the eflluent gases and vapors from zone 34 pass through zone 32 into a common outlet conduit 36. The Hydrocracking Zones are connected together for sequential flow of unconverted feedstock by connecting pipes 38. Each zone downstream .is maintained at a somewhat higher temperature than the preceding zone so that there is a temperature gradient between the first and the last of the zones. Hydrogen gas is furnished to the Hydrocracking Zones via a main inlet conduit 37 and a manifold 39 leading to the bottom of each of the vessels 30. The temperature, pressure, and other conditions are the same as those recited in the description of the Hydrocracking Zone of FIGURE 1.

Coal extract and molten zinc chloride, free of oxide, are introduced through conduits 40 and 42, respectively, into a conduit 44 leading to the first of the Hydrocracking Zones 32. The nondistillable coal extract is partially converted to vaporous distillate which is withdrawn through the outlet conduit 36. The unconverted portion of the coal extract is transferred by conduit 38 to the next Hydrocracking Zone 32, and so on until the last zone 32 has been reached, and thence on sequentially through the lower Hydrocracking Zones .34. At the last zone 34, the liquid mixture comprises mostly spent catalyst, organic r id e and even carbon. This mixture is sent to a Regeneration Zone through a discharge pipe 46.

The effluent gases and vapors withdrawn through the common conduit 36 are passed through a slurry of molten zinc chloride and zinc oxide contained in a vessel 48. This vessel is continuously supplied with the slurry via a conduit 50. The zinc oxide in the slurry absorbs H'Cl contained in the efliuent gases. HCl-free gas is recovered through a conduit 52. The slurry of ,zinc chloride and zinc oxide is conducted through a main conduit 54 to two separate manifold lines 56 and 58, respectively, which supply zinc-oxide and supplemental fresh zinc chloride catalyst to each of the Hydrocracking Zones. The zinc oxide serves as an acceptor for most of the HCl generated, the residual HCl being absorbed asmentioned in the cleanup absorption vessel 48.

FIGURE 3 shows a simple version of a regeneration scheme based on oxidation at elevated temperatures of sulfur, carbon and nitrogen components in a liquid phase process. The reactions occurring in sucha regeneration process are as follows:

Spent catalyst containing ZnCl ZnCl -Nl-I Z113, and

regenerated catalyst to the Hydrocracking Zone, The

products of oxidation, i.-e.,. flue gas, are discharged via a conduit 76 from the combustion tower 62.

FIGURE 4 shows another process .ior regenerating spent catalyst from the Hydrocracking Zone. According to this process, the entire spent catalyst is incinerated at high temperatures by combustion of the carbon .and sulfur components of the molten catalyst, and any residual ammonia that may have remained in the melt as well. This process is applicable to those cases where the coke yield is relatively high, of the order of 3 percent or more by weight of the coal extract. Under these conditions, the heat of combustion of the spent catalyst is sufficient to vaporize all of the zinc chloride present in the spent melt. Thus, it is possible to inject the melt into a fluid bed of carbon and volatilize all of the zinc chloride while burning carbon and sulfur in solid form.

Referring to FIGURE 4, spent catalyst from the Hydrocracking Zone is introduced via a conduit into a combustion zone 82. The carbon, sulfur, and any nitrogen components in the spent catalyst a-re oxidized by air fed to the combustion zone via conduit 84.. The heat developed in this zone is sufficient to vaporize all the zinc chloride. The latter in vapor form, together with entrained zinc' oxide, is withdrawn through a conduit 86 to a combined condenser and scrubber 88. A portion of the zinc chloride is condensed The condensate and zinc oxide form a slurry which is discharged through a conduit to a heat exchanger 92 for cooling to a temperature between about 1000 and 1100 F. The cooled 'ZnO slurry in ZnCl; is returned to the Hydrocracking Zone through conduits 94 and 96. A portion, however, is recycled via a conduit 98 to the condenser-scrubber 8.8 to condense the solidsladen vapors from the combustion vessel 82.

ZnCI vapors and noncondensable gases, i.e., C0, C0 N and HCl are withdrawn from the condenser 88 through a conduit 100 to another condenser 102 wherein the remaining traces of ZnCl are condensed. The pure ZnCl melt is discharged through a conduit to a cooler 106, and thence through a conduit 108 back to the Hydrocracking Zone. A portion of the cooled melt isrccirculated to the condenser 102 via a conduit 110..

Noncondensable gas, including HCl, is withdrawn from the condenser 102 through a conduit 112. A slip-stream of 2110 in ZnCl slurry from conduit ,98 is introduced into conduit 112, to provide ZnO to neutralize any HCl, thus forming some ZnCl Any ZnCl so formed is cooled in a heat exchanger 114 and carried via conduit 116 to a condenser 118 where the ZnCl is condensed, The noncondensable gases are discharged via conduit 120. The ZnCl melt at this point may contain some ash or contaminant solids. Accordingly, the melt is withdrawn via a conduit 122 to a filter 124 where the ash is separated and discharged through a conduit 126. The ZnCl melt is transported via conduits 128 and 96 back to the Hydrocracking Zone. ZnO may be added as make-up via conduit 130 to control the ZnO concentration in the ZnCl slurry.

What is claimed is:

1. In the process for converting polynuclear aromatic hydrocarbonaceous feedstock to gasoline by hydrocracking wherein the feedstock is contacted with molten zinc chloride in the presence of hydrogen at elevated tempera: ture and pressure to effect hydrocrac ing of the feedstock,

the improvement which comprises maintaining a mixture of zinc chloride and zinc oxide in a hydrocracking zone, said chloride and oxide being in a mole ratio of at least ten parts chloride to one part oxide. 7

2. The process of claim 1 wherein the feedstock contains appreciable quantities of nitrogen and sulfur compounds.

3. The process of claim 2 in which the feedstock is coal extract.

4. The process of claim 1 wherein spent zinc chloride and zinc oxide is regenerated and returned to the hydrocracking zone.

5. The process of claim 1 wherein efliuent gas from the hydrocracking zone is contacted in a contacting zone with a mixture of zinc chloride and zinc oxide to remove hydrogen chloride gas from the efliuent gas.

6. The process of claim 5 wherein e'fiiuent from said contacting zone is conveyed to said hydrocracking ,zone, said efiiuent comprising zinc chloride and zinc oxide.

7. A process for converting polynuclear aromatic hydrocarbonaceous feedstock to gasoline comprising serialw ly passing said feedstock through a plurality of hydrocracking zones, each zone containing molten zinc chloride, at least one hydrocracking zone downstream from the first zone in said series of zones containing zinc oxide in admixture with said molten zinc chloride, said chloride and oxide being in a mole ratio of at least ten parts chloride to one part oxide; and passing efiiuent gases from downstream zones in said series of zones through upstream zones in said series of zones.

8. The process of claim 7 further comprising contacting efliuent gases from said upstream zones with a slurry of molten zinc chloride and zinc oxide.

9. The process of claim 8 further comprising passing efiluent slurry from said slurry-efiluent gases contacting step to at least one hydrocracking zone downstream from 15 said first zone in said series of zones.

References Cited UNITED STATES PATENTS 1,950,309 3/1934 Jennings 208-100 2,057,629 10/ 1936 Morrell et al. 208-296 2,205,411 6/1940 Howard 208-296 2,749,288 6/ 1956 Watkins 208-125 2,768,935 10/ 1956 Watkins 208-8 FOREIGN PATENTS 193,071 2/ 1923 Great Britain.

DANIEL E. WYMAN, Primary Examiner. P. KONOPKA, Assistant Examiner. 

1. IN THE PROCESS FOR CONVERTING POLYNUCLEAR AROMATIC HYDROCARBONACEOUS FEEDSTOCK TO GASOLINE BY HYDROCRACKING WHEREIN THE FEEDSTOCK IS CONTACTED WITH MOLTEN ZINC CHLORIDE IN THE PRESENCE OF HYDROGEN AT ELEVATED TEMPERATURE AND PRESSURE TO EFFECT HYDROCRACKING OF THE FEEDSTOCK, THE IMPROVEMENT WHICH COMPRISES MAINTAINING A MIXTURE OF ZINC CHLORIDE AND ZINC OXIDE IN A HYDROCRACKING ZONE, SAID CHLORIDE AND OXIDE BEING IN A MOLE RATIO OF AT LEAST TEN PARTS CHLORIDE TO ONE PART OXIDE. 